목적: Intrathoracic lesions in patients head and neck squamous cell carcinomas (HNSCC) may indicate metastasis, second cancers, or benign lesions, and the diagnosis affects therapeutic planning. The current study aimed to compare the diagnostic value of ¹⁸F-FDG PET/CT versus chest CT for assessing intrathoracic lesions in patients with HNSCC. 방법:This prospective study included a total of 389 HNSCC patients who received initial diagnostic evaluation with contrast-enhanced chest CT and ¹⁸F-FDG PET/CT. Histopathological results and follow-up imaging of chest lesions were served as the standard reference. The receiver-operating characteristic curve, McNemars test and logistic regression using generalized estimating equations was utilized to compare the diagnostic value of CT and ¹⁸F-FDG PET/CT. 결과:Of the 389 patients, 145 (37.4%) had the history of inflammatory lung diseases. On a lesion-based analysis, ¹⁸F-FDG PET/CT showed a trend toward a higher sensitivity than chest CT(80.0% vs. 61.9%, P = 0.135). The area under the curve(AUC) for PET/CT was also higher than for chest CT, although not significantly so (0.932 vs. 0.866, P=0.189).On a patient-based analysis, the sensitivity of chest CT was lower than that of PET/CT (66.7% vs. 83.3%, P=0.625).In terms of diagnostic capability, the AUC was higher for PET/CT than chest CT (0.886 vs. 0.813, P=0.355). The maximal standardized uptake value (SUVmax) above the median value (8.7) was significantly associated with comfirmation of thoracic malignancy (P = 0.026) 결론:¹⁸F-FDG PET/CT showed a consistent trend toward higher sensitivity and diagnostic capability than chest CT for the detection of thoracic malignancy in patients with HNSCC. Our data also suggest that SUVmax assessed by PET/CT can provide additional information for the comfirmation of thoracic malignancy with history of inflammatory granulomatous lung disease.